/******** 具有函数提升性质 **********/
//可以先使用再声明，使用时为undefined
console.log(name); //undefined
var name = "zhangsan";
console.log(name); //zhansan

/******** 不受块作用域影响 *******/
for (var i = 0; i < 5; i++) {}
console.log(i); //5

for (let j = 0; j < 5; j++) {}
//j is not defined
// console.log(j);

/****** 可以重复声明 ****/
var a = 10;
a += 5;
console.log(a); //15
var a = 20;
console.log(a); //20
// Identifier 'a' has already been declared
// let a = 25;
// console.log(a);
